Apparatus and method for beamforming in wireless communication system

ABSTRACT

An apparatus and a method for generating a frame for communication using beamforming in a wireless communication system are provided. A method for transmitting a signal in a transmitting stage includes determining a beam change time of a region for transmitting information in a frame, and transmitting the information to a receiving stage over the region for transmitting the information by considering the beam change time. The frame includes a plurality of regions divided based on a type of the information transmitted to the receiving stage, and the plurality of the regions includes different beam change times.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of prior application Ser.No. 15/470,412, filed on Mar. 27, 2017, which is a continuationapplication of prior application Ser. No. 13/560,188, filed on Jul. 27,2012, which has issued as U.S. Pat. No. 9,985,705 on May 29, 2018 and isbased on and claims priority under 35 U.S.C § 119(a) of a Korean patentapplication number 10-2011-0074971, filed on Jul. 28, 2011, in theKorean Intellectual Property Office, and a Korean patent applicationnumber 10-2012-0081790, filed on Jul. 26, 2012, in the KoreanIntellectual Property Office, the disclosure of each of which isincorporated by reference herein in its entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to an apparatus and a method forbeamforming in a wireless communication system. More particularly, thepresent invention relates to an apparatus and a method for generating aframe for communication using beamforming in a wireless communicationsystem.

2. Description of the Related Art

A wireless communication system can enhance a data transfer rate using abeamforming technique. Beamforming is a series of techniques forenhancing transmission and reception performance using a high-gainantenna.

Using beamforming, the wireless communication system needs to reduce anantenna beam width in order to raise the antenna gain. The wirelesscommunication system needs to use a plurality of narrow beams totransmit signals in all directions.

However, since a frame is not defined for the communication usingbeamforming in the wireless communication system, it is required togenerate the frame for the communication by use of beamforming.

The above information is presented as background information only toassist with an understanding of the present disclosure. No determinationhas been made, and no assertion is made, as to whether any of the abovemight be applicable as prior art with regard to the present invention.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address the above-mentionedproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present invention is toprovide an apparatus and a method for generating a frame forcommunication using beamforming in a wireless communication system.

Another aspect of the present invention is to provide an apparatus and amethod for generating a frame for communication using beamforming in awireless communication system which utilizes a plurality of beamformingantennas.

Yet another aspect of the present invention is to provide an apparatusand a method for generating a frame to differently set a beam changetime according to a type of information transmitted using beamforming ina wireless communication system.

Still another aspect of the present invention is to provide an apparatusand a method for generating a frame to adaptively define a pilot patternaccording to a type of information transmitted using beamforming in awireless communication system.

A further aspect of the present invention is to provide an apparatus anda method for determining the number of symbols constituting a slot byconsidering a Cyclic Prefix (CP) length in a wireless communicationsystem.

A further aspect of the present invention is to provide an apparatus anda method for generating a frame such that a symbol at the point of thebeam change uses a long CP in a wireless communication system.

In accordance with an aspect of the present invention, a method fortransmitting a signal in a transmitting stage of a wirelesscommunication system which comprises a plurality of antennas and forms aplurality of beams is provided. The method includes determining a beamchange time of a region for transmitting information in a frame, andtransmitting the information to a receiving stage over the region fortransmitting the information by considering the beam change time,wherein the frame comprises a plurality of regions divided based on atype of the information transmitted to the receiving stage, and whereinthe plurality of the regions comprises different beam change times.

According to another aspect of the present invention, an apparatus fortransmitting a signal in a transmitting stage of a wirelesscommunication system which forms a plurality of beams is provided. Theapparatus includes an antenna unit for comprising a plurality of antennaelements, a Radio Frequency (RF) chain for forming a beam through theantenna unit, and a controller for transmitting information to areceiving stage over a region for transmitting the information byconsidering a beam change time of the region for transmitting theinformation in a frame, wherein the frame comprises a plurality ofregions divided based on a type of the information transmitted to thereceiving stage, and wherein the plurality of the regions comprisesdifferent beam change times.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 illustrates a frame of a wireless communication system accordingto an exemplary embodiment of the present invention;

FIGS. 2A through 2D illustrate a frame of a wireless communicationsystem according to exemplary embodiments of the present invention;

FIGS. 3A and 3B illustrate reference signals of a wireless communicationsystem according to exemplary embodiments of the present invention;

FIG. 4 illustrates resource allocation in a wireless communicationsystem according to an exemplary embodiment of the present invention;

FIG. 5 illustrates a frame of a wireless communication system adoptingFrequency Division Duplexing (FDD) according to an exemplary embodimentof the present invention;

FIG. 6 illustrates a frame of a wireless communication system adoptingTime Division Duplexing (TDD) according to an exemplary embodiment ofthe present invention;

FIG. 7 illustrates a block diagram of a transceiver according to anexemplary embodiment of the present invention;

FIGS. 8A and 8B illustrate a Radio Frequency (RF) chain according toexemplary embodiments of the present invention;

FIG. 9 illustrates an RF chain according to an exemplary embodiment ofthe present invention;

FIG. 10 illustrates a block diagram of a receiving stage according to anexemplary embodiment of the present invention;

FIG. 11 is a flowchart illustrating a method for transmitting a signalusing beamforming in a transmitting stage according to an exemplaryembodiment of the present invention;

FIG. 12 is a flowchart illustrating a method for receiving a signal in areceiving stage according to an exemplary embodiment of the presentinvention;

FIG. 13 is a flowchart illustrating a method for transmitting a signalusing beamforming in a transmitting stage according to an exemplaryembodiment of the present invention; and

FIG. 14 is a flowchart illustrating a method for receiving a signal in areceiving stage according to an exemplary embodiment of the presentinvention.

Throughout the drawings, it should be noted that like reference numeralswill be understood to refer to like parts, components and structures.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but, are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purpose only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

By the term “substantially” it is meant that the recited characteristic,parameter, or value need not be achieved exactly, but that deviations orvariations, including for example, tolerances, measurement error,measurement accuracy limitations and other factors known to those ofskill in the art, may occur in amounts that do not preclude the effectthe characteristic was intended to provide.

An exemplary embodiment of the present invention provides a techniquefor generating a frame for communication using beamforming in a wirelesscommunication system.

Hereinafter, it is assumed that a wireless communication system adoptsan antenna beamforming technique. The antenna beamforming techniqueforms the beam by changing a phase of a radio frequency signaltransmitted and received over each antenna.

FIGS. 1 through 14, discussed below, and the various exemplaryembodiments used to describe the principles of the present disclosure inthis patent document are by way of illustration only and should not beconstrued in any way that would limit the scope of the disclosure. Thoseskilled in the art will understand that the principles of the presentdisclosure may be implemented in any suitably arranged communicationssystem. The terms used to describe various embodiments are exemplary. Itshould be understood that these are provided to merely aid theunderstanding of the description, and that their use and definitions inno way limit the scope of the invention. Terms first, second, and thelike are used to differentiate between objects having the sameterminology and are in no way intended to represent a chronologicalorder, unless where explicitly stated otherwise. A set is defined as anon-empty set including at least one element.

FIG. 1 illustrates a frame of a wireless communication system accordingto an exemplary embodiment of the present invention.

Referring to FIG. 1, the frame includes a plurality of fixed-lengthsubframes, and one subframe includes a plurality of fixed-length slots.One slot includes a plurality of fixed-length symbols. For example, theframe can include 5 subframes, one subframe can include 20 slots, andone slot can include 10 or 11 symbols. In so doing, the number of thesymbols constituting the slot is determined by a length of a CyclicPrefix (CP) of each symbol. For example, when one slot of 50 us includes10 symbols, the length of each symbol is equally 5 us and the CP lengthof each symbol is equally lus. For example, when one slot of 50 usincludes 11 symbols, the length of the first symbol of the slot is 5 usand the remaining 10 symbols are 4.5 us in length. At this time, the CPlength of the first symbol of the slot is lus and the CP length of theremaining 10 symbols is 0.5 us.

The wireless communication system divides the frame into a first slotfor at least one of a synchronization signal and common controlinformation, a training signal slot, a control slot, and a data slot.The slots can be constructed as shown in FIGS. 2A to 2D according toproperties of information transmitted by the corresponding slot. Herein,the first slot can include any one of a slot for the synchronizationsignal and the common control information, a slot for thesynchronization signal, and a slot for the common control information.Hereafter, it is assumed that the first slot is the slot for thesynchronization signal and the common control information.

FIGS. 2A through 2D illustrate a frame of a wireless communicationsystem according to exemplary embodiments of the present invention.

FIG. 2A illustrates a slot for the synchronization signal and the commoncontrol information, FIG. 2B illustrates a subframe for data and controlinformation, FIG. 2C illustrates a control slot, and FIG. 2D illustratesa random access channel slot.

Referring to FIG. 2A, the slot for the synchronization signal and thecommon control information is a minimum unit for carrying thesynchronization signal and the common control information in the frameand is located in a designated region of the frame. A transmitting stagerepeatedly transmits the synchronization signal and the common controlinformation while changing the beam per antenna beam within the slot forthe synchronization signal and the common control information so that areceiving stage can receive the synchronization signal and the commoncontrol information at any location in the cell. For example, when theslot #2 of the subframe #0 of FIG. 1 is the slot for the synchronizationsignal and the common control information, the transmitting stagetransmits the synchronization signal and the common control informationover the slot #2 of the subframe #0 of each frame. In so doing, thetransmitting stage transmits the synchronization signal and the commoncontrol information with the transmit beam #0 using the symbols #0 and#1, transmits the synchronization signal and the common controlinformation with the transmit beam #1 using the symbols #2 and #3, andtransmits the synchronization signal and the common control informationwith the transmit beam #2 using the symbols #4 and #5. Herein, thecommon control information includes control information transmitted onthe frame basis, such as cell identifier, system, and cell common systeminformation for the cell access and migration of the receiving stage,and frame configuration information. For example, according to the 3rdGeneration Partnership Project (3GPP) standard, the common controlinformation includes part or all of a Master Information Block (MIB), aSystem Information Block (SIB) 1, and an SIB 2. That is, the commoncontrol information includes the number of antenna layers, a downlinkbandwidth, a base station and cell identifiers, a Public Land MobileNetwork (PLMN) identifier, an uplink frequency, an uplink bandwidth, aduplex type, random access resource allocation information, and a framenumber.

The transmitting stage transmits the synchronization signal and thecommon control information, either of which including the beamidentifier, so that the receiving stage can identify the beam forreceiving the synchronization signal and the common control information.For example, when the synchronization signal carries the beamidentifier, the transmitting stage does not have to successivelytransmit the synchronization signal and the common control information.That is, the transmitting stage can transmit the common controlinformation over the other fixed slot which does not adjoin thesynchronization signal. For example, when the common control informationcarries the beam identifier, the transmitting stage needs toconsecutively transmit the synchronization signal and the common controlinformation.

As stated above, while the transmission location of the synchronizationsignal is fixed in the frame, the number of the slots for thesynchronization signal and the common control information can vary. Forexample, the number of the slots for the synchronization signal and thecommon control information can differ according to the number of thetransmit beams of the transmitting stage.

Referring to FIG. 2B, at least one slot is allocated to the controlslot, in one subframe, for carrying the control information and otherslots are allocated to the data slots for carrying data. Herein, thenumber of the control slots and the data slots in the subframe candiffer per subframe.

All of the symbols in one data slot use the same beam. When the dataslot is changed, the beam for transmitting the data can alter. Forexample, the transmitting stage transmits data over the slot #1 usingthe beam #3 and the slots #2 and #3 using the beam #0. That is, theminimum unit for carrying user data with the same beam is defined as theslot. Accordingly, one slot can be set to one Transmission Time Interval(TTI) so that the receiving stage, receiving merely one slot, can decodethe data.

When the slot #0 is allocated to the control slot in the subframe ofFIG. 2B, the control slot (the slot #0) is constituted as shown in FIG.2C.

Referring to FIG. 2C, the control slot can change the beam carrying thecontrol information based on at least one symbol. For example, thetransmitting stage transmits the control information over the symbol #0using the beam #3, the symbol #1 using the beam #0, and the symbol #9using the beam #5. Herein, the control information includes the resourceallocation information for the data transmission.

Referring to FIG. 2D, every resource in one slot can be allocated to therandom access channel slot. At this time, the resource allocationinformation of the random access channel slot is carried by the commoncontrol information to the receiving stage.

Using the random access channel slot, the receiving stage transmits arandom access preamble and a random access information signal. When thereceiving stage knows an optimum transmit beam of the transmittingstage, the receiving stage transmits the random access preamble and therandom access information signal just once using the optimum transmitbeam. By contrast, when not knowing the optimum transmit beam of thetransmitting stage, the receiving stage repeatedly transmits the randomaccess preamble and the random access information signal while changingthe transmit beam direction. Herein, the random access preambleindicates a signal for detecting synchronization of the uplink signal.The random access information signal includes receiving stageinformation including the transmit beam identifier of the receivingstage.

The transmitting stage receives the random access signal using one beamwithin one slot. When the slot is changed, the transmitting stagereceives the random access signal by changing the beam. Herein, therandom access signal includes the random access preamble and the randomaccess information signal.

In this exemplary embodiment, the random access channel slot uses theresources of one slot. Alternatively, the random access channel slot mayuse part of the resources of the data slot.

In the frame of the wireless communication system, the beam change timediffers according to the channel type. The frame can be constructed suchthat the symbol of the long CP can be positioned at the point of thebeam change. For example, as the control slot of FIG. 2C can change thebeam based on at least one symbol, the long CP (lus) is used per symbol.Accordingly, the control slot can include 10 symbols based on the longCP Similarly to the control slot, the slot for the synchronizationsignal and the control signal and the training signal slot, which canchange the beam based on at least one symbol, can apply the long CP persymbol. For example, the data slot of FIG. 2B, which can change the beambased on the slot, utilizes the long CP (lus) in its first symbol. In sodoing, the other symbols of the data slot excluding the first symbol canapply the short CP (0.5 us) to increase the transmission efficiency orthe long CP (lus) in the light of the channel properties. When the othersymbols of the data slot excluding the first symbol use the short CP,the data slot can include 11 symbols. By contrast, when the othersymbols of the data slot excluding the first symbol use the long CP, thedata slot can include 10 symbols.

As such, each symbol can include the CP of the different lengths.However, the frame includes the slots of the same length. Hence, theframe can be constituted such that the slots including the symbols ofthe different CP lengths can coexist. In this case, the frame canselectively use the CP of the optimum length based on the channelproperties and the beam change time.

As described so far, the data slot and the control slot have differentunits for the beam change. Thus, the transmitting stage can transmit areference signal, such as pilot as shown in FIGS. 3A and 3B.

FIGS. 3A and 3B illustrate reference signals of a wireless communicationsystem according to exemplary embodiments of the present invention.

FIG. 3A illustrates a reference signal of a data slot, and FIG. 3Billustrates a reference signal of a control slot. The data slot isassumed to include 11 symbols.

Referring to FIG. 3A, the data slot, which changes the beam based on theslot, generates the reference signal based on the slot. For example, thedata slot can carry four independent Quadrature Amplitude Modulation(QAM) or Phase Shift Keying (PSK) symbols together in the subcarrier ofeach symbol.

Referring to FIG. 3B, the control slot, which changes the beam based onat least one symbol, generates the reference signal based on at leastone symbol.

With the frame as constructed above, the resources can be allocated asshown in FIG. 4.

FIG. 4 illustrates resource allocation in a wireless communicationsystem according to an exemplary embodiment of the present invention.

Referring to FIG. 4, a transmitting stage can allocate the resources ofthe data slots #4, #5 and #6 to the receiving stage #3 using the beam #1and allocate the resources of the data slots #7 and #8 to the receivingstage #4 using the beam #1.

In addition, the transmitting stage can allocate the resources of theslots #9 through #13 to the receiving stages #5 and #6 using the beam#4. The resources of the slots #9 through #13 allocated to the receivingstages #5 and #6 are distinguished as different frequency resources.

When a Frequency Division Duplexing (FDD) frame is generated using theframe structure as above, the wireless communication can generate an FDDframe as shown in FIG. 5.

FIG. 5 illustrates a frame of a wireless communication system adoptingFDD according to an exemplary embodiment of the present invention.

Referring to FIG. 5, according to FDD, the downlink and the uplinkoccupy different frequency resources. Hence, the FDD frame is generatedsuch that a downlink frame and an uplink frame occupy differentfrequencies.

The downlink frame and the uplink frame each include 5 subframes, andone subframe includes 20 slots. One slot includes 10 or 11 symbols.

The downlink frame allocates the slot #0 of each subframe to the controlslot and allocates the slot #2 of the subframe #0 to the synchronizationsignal and common control information slot.

The downlink frame allocates the slot #5 of each subframe to thetraining signal slot and allocates the other slots to the data slots.

The uplink frame allocates the slot #0 of each subframe to the controlslot and allocates the other slots to the data slots. Herein, thecontrol information transmitted by the receiving stage over the uplinkcontrol slot includes Hybrid Automatic Repeat reQuest (HARQ)ACKnowledgment/Non-ACKnowledgment (ACK/NACK) information, ChannelQuality Indicator (CQI) feedback information, Precoding Matrix Indicator(PMI) information, rank indicator information, scheduling requestinformation, transmit beam information of the base station, and trainingsignal request information.

The wireless communication system can generate a Time Division Duplexing(TDD) frame as shown in FIG. 6.

FIG. 6 illustrates a frame of a wireless communication system adoptingTDD according to an exemplary embodiment of the present invention.

Referring to FIG. 6, according to TDD, the downlink and the uplinkoccupy different time resources. Hence, the TDD frame divides a downlinkframe and an uplink frame with time resources.

The TDD frame includes 5 subframes, and one subframe includes 20 slots.One slot includes 10 or 11 symbols.

In one subframe, the slots #0 through #10 are allocated to the downlinkframe and the slots #11 through #19 are allocated to the uplink frame.

The downlink frame allocates the slot #0 of each subframe to thedownlink control slot and allocates the slot #2 of the subframe #0 tothe synchronization signal and common control information slot.

The downlink frame allocates the slot #5 of each subframe to thetraining signal slot and allocates the other slots to the data slots.

The uplink frame allocates the slot #11 of each subframe to the uplinkcontrol slot and allocates the other slots to the data slots.

The slot #10 of each subframe is used as the CP for the operationswitch. The CP for the operation switch, which is not shown in thedrawing, is interposed between the subframes.

As such, the training signal slot is allocated to select the narrow beamwhich is used to transmit and receive the data. Within the trainingsignal slot, the transmitting stage can change the beam direction basedon at least one symbol. Herein, the training signal slot is periodicallyallocated to the fixed position as shown in FIGS. 5 and 6, or may beaperiodically allocated according to the request of the receiving stage.

The synchronization signal carries the beam identifier using part of thesynchronization signal code or using the common control information.Rather than directly carrying the beam identifier, the training signalcan indirectly notify the beam identifier using the location and theorder of the training signal in the training signal slot.

The training signals in the training signal slot should be selected tominimize inter-cell interference. For example, the training signals arearranged at regular subcarrier intervals like the reference signal ofFIG. 3B, and the location of the training signal varies in each cell.For example, the training signal sequence may be generated orthogonallyaccording to the cell identifier so as to mitigate the interference.

The wireless communication system can provide a communication serviceusing a plurality of different bandwidths. Hence, the frame of thewireless communication system needs to be designed to support themultiple bandwidths.

To support the bandwidths, the frame is to be designed such that thesynchronization signal and the common control information aretransmitted using the minimum bandwidth and the other signals occupy thewhole frequency band. For example, when supporting the bandwidth 1 GHzwith 16 Resource Blocks (RBs), the wireless communication system cansupport four bandwidths of 125 MHz, 250 MHz, 500 MHz, and 1 GHz. Thus,the frame allocates the synchronization signal and the common controlinformation to two central RBs corresponding to the minimum bandwidth125 MHz and allocates the other signals to the whole band of 1 GHz.

As such, the control slot for the control information is separatelyprovided. When the amount of the control information transmitted by thetransmitting stage matches the multiple of the resource amount of theslot, unnecessary resource waste of the control slot does not occur.However, when the amount of the control information transmitted by thetransmitting stage does not match the multiple of the resource amount ofthe slot, the control slot causes the unnecessary resource waste. Forexample, when one slot includes 10 symbols and the transmitting stagerequires 12 symbols to transmit the control information, the frameallocates two slots to the control slots. In this case, eight symbols ofthe second control slot can be unnecessarily wasted.

To reduce the resource waste of the control slot, when the amount of thecontrol information transmitted by the transmitting stage does not matchthe multiple of the resource amount of the slot, the transmitting stagecan transmit the control information by puncturing part of the dataslot. When the reference signal of the data slot is punctured totransmit the control information, the channel estimation performance ofthe receiving stage can be degraded. Hence, the transmitting stage canalleviate the performance degradation caused by the puncturing by evenlydistributing the reference signal over the slot as shown in FIG. 3A.

In this exemplary embodiment, the transmitting stage punctures the dataslot for the control information. Similarly, the transmitting stage maytransmit the synchronization signal and the common control informationor the training signal by puncturing the data slot.

FIG. 7 illustrates a block diagram of a transceiver according to anexemplary embodiment of the present invention.

Referring to FIG. 7, the transceiver includes a controller 700, a beamselector 710, an antenna unit 720, a transmitter 730, and a receiver740.

The controller 700 controls the operations of the transceiver.

According to any one of the frame structures of FIGS. 1, 5, and 6, thecontroller 700 forms the beam to transmit the synchronization signal andthe common control information, the control information, the trainingsignal, and the data. For example, the controller 700 transmits thesynchronization signal and the common control information over thesynchronization signal and common control information slot positioned inthe designated region of the frame. In so doing, the controller 700repeatedly transmits the synchronization signal and the common controlinformation while changing the beam per antenna beam within thesynchronization signal and common control information slot as shown inFIG. 2A. The controller 700 transmits the synchronization signal and thecommon control information, either including the beam identifier, sothat the receiving stage can identify the beam receiving thesynchronization signal and the common control information.

For example, the controller 700 changes the beam based on the slot inthe region allocated to the data slot in the subframe as shown in FIG.2B. In so doing, the controller 700 transmits the reference signal basedon the slot in the data slot as shown in FIG. 3A.

For example, the controller 700 changes the beam based on at least onesymbol in the region allocated to the control slot of the subframe asshown in FIG. 2C. In so doing, the controller 700 transmits thereference signal based on at least one symbol in the control slot asshown in FIG. 3B.

For example, when receiving the random access signal over the randomaccess channel slot allocated as shown in FIG. 2D, the controller 700receives the random access signal using one beam within one slot. Whentransmitting the random access signal over the random access channelslot, the controller 700 transmits the random access signal once usingthe optimum transmit beam to carry the random access signal. When notknowing the optimum transmit beam, the controller 700 repeatedlytransmits the random access signal by changing the transmit beamdirection.

For example, the controller 700 transmits the training signal over thetraining signal slot of the fixed location. The training signal slot maybe aperiodically allocated. The controller 700 may change the beam basedon at least one symbol within the training signal slot.

For example, the controller 700 may transmit at least one of the controlinformation, the synchronization signal and the common controlinformation, and the training signal by puncturing part of the dataslot. In so doing, the controller 700 transmits the puncturinginformation of the data slot to the receiving stage using the controlinformation.

The beam selector 710 selects the beam of the corresponding patternunder the control of the controller 700. In the transmit beamforming,the beam selector 710 sends the selected beam pattern information to thetransmitter 730. In the receive beamforming, the beam selector 710 sendsthe selected beam pattern information to the receiver 740.

The antenna unit 720 includes a plurality of antenna elements. Forexample, the antenna unit 720 includes a plurality of omnidirectionalantenna elements as shown in FIGS. 8A and 8B. For example, the antennaunit 720 may include a plurality of directional antenna elements fortransmitting the signal in different directions as shown in FIG. 9.

The transmitter 730 includes a transmission modem 732 and a transmissionRF chain 734.

The transmission modem 732 encodes and modulates data to transmit to thereceiving stage over the antenna, and converts the modulated signal toan analog signal. The transmission modem 732 sends the analog-basebandsignal to the transmission RF chain 734.

The transmission RF chain 734 includes a plurality of RF paths fordelivering the signals to the antenna elements. In so doing, thetransmission RF chain 734 can use only some antenna elements and some RFpaths according to the beam pattern and the beam width selected by thebeam selector 710.

FIGS. 8A and 8B illustrate a Radio Frequency (RF) chain according toexemplary embodiments of the present invention and FIG. 9 illustrates anRF chain according to an exemplary embodiment of the present invention.

Referring to FIGS. 7, 8A, 8B, and 9, the transmission RF chain 734multiplexes the baseband signal output from the transmission modem 732to at least one RF path activated, converts the corresponding basebandsignal to an RF signal in each RF path, and transmits the signal throughthe antenna unit 720. In so doing, the transmission RF chain 734controls the baseband signal to form the beam in the beam patternselected by the beam selector 710. For example, when the antenna unit720 includes the omnidirectional antenna elements as shown in FIG. 8A,the transmission RF chain 734 includes phase shifters 800-1 through800-N for changing the phase of the signal transmitted in the RF path ofeach antenna element 810-1 through 810-N. The phase shifters 800-1through 800-N change the phase of the signal to transmit through eachantenna element according to the beam pattern and the beam widthselected by the beam selector 710.

For example, when the antenna unit 720 includes the multiple directionalantenna elements 910-1 through 910-N as shown in FIG. 9, thetransmission RF chain 734 includes a switch 900 which interconnects thetransmission modem 732 and the antenna element according to the beampattern. The switch 900 interconnects at least one antenna element andthe transmission modem 732 according to the beam pattern and the beamwidth selected by the beam selector 710. Herein, the switch 900 caninterconnect one transmission modem 732 and at least one antennaelement.

The receiver 740 includes a reception RF chain 742 and a reception modem744.

The reception RF chain 742 includes a plurality of RF paths for the RFsignals received via the antenna elements. In so doing, the reception RFchain 742 can use only some antenna elements and some RF paths accordingto the beam pattern and the beam width selected by the beam selector710.

The reception RF chain 742 converts the RF signals received from theantenna elements to the baseband signals and sends the baseband signalsto the reception modem 744. In so doing, the reception RF chain 742controls the baseband signal to form the beam in the beam patternselected by the beam selector 710. For example, when the antenna unit720 includes the multiple omnidirectional antenna elements as shown inFIG. 8B, the reception RF chain 742 includes phase shifters 820-1through 820-N for changing the phase of the signals received through theantenna elements 810-1 through 810-N. The phase shifters 820-1 through820-N change the phase of the signals received through the antennaelements according to the beam pattern and the beam width selected bythe beam selector 710.

For example, when the antenna unit 720 includes the directional antennaelements 910-1 through 910-N as shown in FIG. 9, the reception RF chain742 includes a switch 900 which interconnects the reception modem 744and the antenna element according to the beam pattern. The switch 900interconnects at least one antenna element and the reception modem 744according to the beam pattern and the beam width selected by the beamselector 710. Herein, the switch 900 can interconnect one receptionmodem 744 and at least one antenna element.

The reception modem 744 converts the analog signal output from thereception RF chain 742, to a digital signal, and demodulates and decodesthe digital signal.

In this exemplary embodiment, the transceiver shares the single antennaunit 720. Alternatively, the transmitter and the receiver can employdifferent antenna units. Alternatively, the transmitter and the receivermay be separate modules.

As stated above, the antenna unit 720 of FIG. 8A or 8B changes the phaseof each antenna element or changes the switch according to the structureof FIG. 9. In the process of changing the phase or the switch, theantenna unit 720 is subject to time delay for stabilization because ofphysical limits of the element. Thus, to mitigate the interference fromthe beam change of the antenna unit 720, the transmitting stage can usethe symbol of the long CP at the point of the beam change.

FIG. 10 illustrates is a block diagram of a receiving stage according toan exemplary embodiment of the present invention.

Referring to FIG. 10, the receiving stage includes a duplexer 1001, areceiver 1003, a controller 1005, a beam selector 1007, and atransmitter 1009.

The duplexer 1001 transmits the transmit signal output from thetransmitter 1009 over the antenna and provides the received signal fromthe antenna to the receiver 1003 according to the duplexing manner.

The receiver 1003 converts the RF signal fed from the duplexer 1001 tothe baseband signal and demodulates the baseband signal. For example,the receiver 1003 can include an RF processing block, a demodulationblock, a channel decoding block, and a message processing block. The RFprocessing block converts the RF signal fed from the duplexer 1001 tothe baseband signal. The demodulation block extracts the data from eachsubcarrier by applying Fast Fourier Transform (FFT) to the signal outputfrom the RF processing block. The channel decoding block includes ademodulator, a deinterleaver, and a channel decoder. The messageprocessing block extracts the control information from the receivedsignal and provides the extracted control information to the controller1005.

The controller 1005 controls the operations of the receiving stage. Forexample, the controller 1005 acquires the synchronization with the basestation by detecting the transmit beam of the transmitting stage of themaximum receive power using the synchronization signals periodicallyreceived from the transmitting stage over the synchronization signal andcommon control information slot. The controller 1005 initially accessesthe transmitting stage by receiving the common control information fromthe transmitting stage through the detected transmit beam of thetransmitting stage.

For example, the controller 1005 controls the beam selector 1007 toselect the beam for receiving the data.

For example, the controller 1005 receives the control information andthe data through the beam selected by the beam selector 1007. Thecontroller 1005 estimates the channel using the reference signal of thecontrol information and the data. For example, the controller 1005estimates the channel using the slot-based reference signal of the dataas shown in FIG. 3A. For example, the controller 1005 may estimate thechannel using the symbol-based reference signal of the controlinformation as shown in FIG. 3B. That is, the controller 1005 estimatesthe channel using the reference signal received through the beamselected by the beam selector 1007 from the reference signal transmittedby the transmitting stage by changing the beam per symbol in the controlslot.

The controller 1005 transmits the control information over the controlslot of the uplink frame and to transmit the data over the data slot tothe transmitting stage. The control slot of the uplink frame isgenerated as shown in FIG. 2C, and the data slot is generated as shownin FIG. 2B.

The beam selector 1007 selects the optimum beam to receive the controlinformation and the data using the training signals provided from thetransmitting stage over the training signal slot. For example, the beamselector 1007 selects the transmit beam of the transmitting stage fortransmitting the control information and the data using the trainingsignals, and the receive beam for receiving the control information andthe data from the transmitting stage.

The transmitter 1009 encodes and converts the data and a control messageto be sent to the transmitting stage, to an RF signal and outputs the RFsignal to the duplexer 1001. For example, the transmitter 1009 caninclude a message generation block, a channel encoding block, amodulation block, and an RF processing block.

The message generation block generates the control message includinginformation of the narrow beam selected by the beam selector 1007. Forexample, the message generation block generates the control messageincluding the beam information selected by the beam selector 1007. Inanother example, the message generation block generates at least onecontrol message of the control information, a sounding signal, and thetraining signal request information to send over the uplink controlslot.

The channel encoding block includes a modulator, an interleaver, and achannel encoder. The modulation block maps the signal output from thechannel encoding block to carriers using Inverse FFT (IFFT). The RFprocessing block converts the baseband signal output from the modulationblock to the RF signal and outputs the RF signal to the duplexer 1001.

FIG. 11 is a flowchart illustrating a method for transmitting a signalusing beamforming in a transmitting stage according to an exemplaryembodiment of the present invention.

Referring to FIG. 11, the transmitting stage transmits thesynchronization signal and the common control signal to the receivingstage over the synchronization signal and common control informationslot in step 1101. For example, the transmitting stage transmits thesynchronization signal and the common control information over thesynchronization signal and common control information slot which isfixed in the frame. In so doing, the transmitting stage repeatedlytransmits the synchronization signal and the common control informationper antenna beam within the synchronization signal and common controlinformation slot as shown in FIG. 2A, so that the synchronization signaland the common control information can be received at any locationwithin the cell. Herein, either the synchronization signal or the commoncontrol information includes the beam identifier.

In step 1103, the transmitting stage sends the training signal over thetraining signal slot. For example, the transmitting stage sends thetraining signal by changing the beam direction in every direction fortransmitting the data.

In step 1105, the transmitting stage determines whether beam selectioninformation is received from the receiving stage. Herein, the beamselection information includes the information of the narrow beamselected by the receiving stage. For example, the transmitting stagedetermines whether the beam selection information is received over theuplink control slot.

Upon receiving the beam selection information, the transmitting stageidentifies the narrow beam selected by the corresponding receiving stagein the beam selection information in step 1107.

In step 1109, the transmitting stage transmits the control informationof the receiving stage and the data using the narrow beam selected bythe receiving stage. For example, the transmitting stage transmits thecontrol information of the receiving stage and the data over the controlslot and the data slot of FIGS. 2B and 2C. In so doing, the transmittingstage adds the reference signal to the data based on the slot as shownin FIG. 3A, and adds the reference signal to the control informationbased on at least one symbol as shown in FIG. 3B. Herein, the controlinformation includes the HARQ ACK/NACK information, power controlinformation, paging information, resource allocation information, asignal transmission scheme, transmit beam information, and trainingsignal slot information. Next, the transmitting stage completes thisprocess.

In this exemplary embodiment, upon determining that the beam selectioninformation is not received, the transmitting stage waits to receive thebeam selection information. Alternatively, upon determining that thebeam selection information is not received within a reference time, thetransmitting stage may re-transmit the training signal.

Now, an exemplary method of the receiving stage for receiving the signalbeamformed by the transmitting stage is explained.

FIG. 12 is a flowchart illustrating a method for receiving a signal in areceiving stage according to an exemplary embodiment of the presentinvention.

Referring to FIG. 12, the receiving stage acquires the synchronizationwith the transmitting stage in step 1201. For example, the receivingstage acquires the synchronization with the transmitting stage bydetecting the transmit beam of the transmitting stage of the maximumreceive power using the synchronization signals periodically receivedfrom the transmitting stage over the synchronization signal and commoncontrol information slot.

In step 1203, the receiving stage confirms the common controlinformation received from the transmitting stage. For example, thereceiving stage receives the common control information from thetransmitting stage over the synchronization signal and common controlinformation through the transmit beam of the transmitting stage detectedin step 1201.

In step 1205, the receiving stage determines whether the training signalis received. For example, the receiving stage determines whether thetraining signal is received over the training signal slot.

Upon receiving the training signal, the receiving stage selects thenarrow beam to be used to receive the data and transmits the data to thetransmitting stage in step 1207. In so doing, the receiving stageselects the transmit beam of the transmitting stage for transmitting thecontrol information and the data using the training signals, and thereceive beam for receiving the control information and the data from thetransmitting stage.

In step 1209, the receiving stage receives the control information andthe data through the narrow beam. In so doing, the receiving stagereceives the control information and the data over the control slot andthe data slot of FIGS. 2B and 2C. For example, the receiving stageconfirms the data slot and the resource allocation information in thecontrol information received over the control slot. Next, the receivingstage receives the data using the data slot and the resource allocationinformation. At this time, the receiving stage can estimate the channelusing the reference signal of the control information and the data. Forexample, the receiving stage estimates the channel using the slot-basedreference signal of the data as shown in FIG. 3A. For example, thereceiving stage may estimate the channel using the symbol-basedreference signal of the control information as shown in FIG. 3B. Thatis, the receiving stage estimates the channel using the reference signalreceived through the beam selected in step 1207 among the referencesignals transmitted by the transmitting stage by changing the beam persymbol in the control slot. Next, the receiving stage completes thisprocess.

In this exemplary embodiment, the receiving stage receives the signalfrom the transmitting stage. When the receiving stage has controlinformation and data to transmit to the transmitting stage, thereceiving stage transmits to the transmitting stage the controlinformation over the control slot of the uplink frame of FIG. 5 or 6,and the data over the data slot.

In this exemplary embodiment, the receiving stage transmits the selectednarrow beam information to the transmitting stage using the trainingsignal.

Alternatively, the transmitting stage may transmit the training signalusing a vertical beam and a horizontal beam as shown in FIG. 13. In thiscase, the receiving stage can transmit its selected vertical beam andhorizontal beam information to the transmitting stage so that thetransmitting stage can select the narrow beam. Herein, the vertical beamindicates the narrow and vertically long beam, and the horizontal beamindicates the short and wide beam.

FIG. 13 is a flowchart illustrating a method for transmitting a signalusing beamforming in a transmitting stage according to an exemplaryembodiment of the present invention.

Referring to FIG. 13, the transmitting stage transmits thesynchronization signal and the common control signal to the receivingstage over the synchronization signal and common control informationslot in step 1301. For example, the transmitting stage transmits thesynchronization signal and the common control information over thesynchronization signal and common control information slot which isfixed in the frame. In so doing, the transmitting stage repeatedlytransmits the synchronization signal and the common control informationper antenna beam within the synchronization signal and common controlinformation slot as shown in FIG. 2A, so that the synchronization signaland the common control information can be received at any locationwithin the cell. Herein, either the synchronization signal or the commoncontrol information includes the beam identifier.

In step 1303, the transmitting stage sends the training signal over thetraining signal slot. For example, the transmitting stage sends thetraining signal by changing the beam direction in every direction fortransmitting the data. The transmitting stage sends the training signalby altering the directions of the vertical beam and the horizontal beam.

In step 1305, the transmitting stage determines whether training signalreception information is received from the receiving stage. Herein, thetraining signal reception information includes information of theoptimum vertical beam and the optimum horizontal beam selected by thecorresponding receiving stage. The optimum vertical beam indicates thevertical beam of the maximum receive power among the vertical beamsreceived at the receiving stage, and the optimum horizontal beamindicates the horizontal beam of the maximum receive power among thehorizontal beams received at the receiving stage.

Upon receiving the training signal reception information, thetransmitting stage selects the narrow beam to be used to transmit thecontrol information and the data to the receiving stage, using theoptimum vertical beam and horizontal beam which are selected by thereceiving stage and contained in the training signal receptioninformation in step 1307. For example, the transmitting stage selectsthe narrow beam overlapping between the optimum vertical beam and theoptimum horizontal beam selected by the receiving stage, as the narrowbeam to be used to transmit the control information and the data to thereceiving stage.

In step 1309, the transmitting stage transmits the control informationof the receiving stage and the data using the selected narrow beam. Forexample, the transmitting stage transmits the control information of thereceiving stage and the data over the control slot and the data slot ofFIGS. 2B and 2C. In so doing, the transmitting stage adds the referencesignal to the data based on the slot as shown in FIG. 3A, and adds thereference signal to the control information based on at least one symbolas shown in FIG. 3B. Next, the transmitting stage completes thisprocess.

In this exemplary embodiment, upon determining that the training signalreception information is not received, the transmitting stage waits toreceive the training signal reception information. Alternatively, upondetermining that the training signal reception information is notreceived within a reference time, the transmitting stage may re-transmitthe training signal.

FIG. 14 is a flowchart illustrating a method for receiving a signal in areceiving stage according to an exemplary embodiment of the presentinvention.

Referring to FIG. 14, the receiving stage acquires the synchronizationwith the transmitting stage in step 1401. For example, the receivingstage acquires the synchronization with the base station by detectingthe transmit beam of the transmitting stage of the maximum receive powerusing the synchronization signals periodically received from thetransmitting stage over the synchronization signal and common controlinformation slot.

In step 1403, the receiving stage confirms the common controlinformation received from the transmitting stage. For example, thereceiving stage receives the common control information from thetransmitting stage over the synchronization signal and common controlinformation slot through the transmit beam of the transmitting stagedetected in step 1401.

In step 1405, the receiving stage determines whether the training signalis received. For example, the receiving stage determines whether thetraining signal is received over the training signal slot.

Upon receiving the training signal, the receiving stage transmits thetraining signal reception information to the transmitting stage in step1407. For example, the transmitting stage transmits the training signalssequentially using the vertical beam and the horizontal beam by changingthe beam direction. In this case, the receiving stage transmits thesignal to the transmitting stage by selecting the optimum vertical beamfrom the vertical beams and the optimum horizontal beam from thehorizontal beams. Herein, the optimum vertical beam indicates thevertical beam of the maximum receive power among the vertical beams, andthe optimum horizontal beam indicates the horizontal beam of the maximumreceive power among the horizontal beams.

In step 1409, the receiving stage selects the narrow beam to be used toreceive the control information and the data using the optimum verticalbeam and the optimum horizontal beam. For example, the receiving stageselects the narrow beam overlapping between the optimum vertical beamand the optimum horizontal beam, as the narrow beam to be used toreceive the data. In so doing, the receiving stage selects the transmitbeam of the transmitting stage for transmitting the control informationand the data using the training signals, and the receive beam forreceiving the control information and the data from the transmittingstage.

In step 1411, the receiving stage receives the control information andthe data through the narrow beam. In so doing, the receiving stagereceives the control information and the data over the control slot andthe data slot of FIGS. 2B and 2C. For example, the receiving stageconfirms the data slot and the resource allocation information in thecontrol information received over the control slot. Next, the receivingstage receives the data using the data slot and the resource allocationinformation. At this time, the receiving stage can estimate the channelusing the reference signal of the control information and the data. Forexample, the receiving stage estimates the channel using the slot-basedreference signal of the data as shown in FIG. 3A. For example, thereceiving stage may estimate the channel using the symbol-basedreference signal of the control information as shown in FIG. 3B. Thatis, the receiving stage estimates the channel using the reference signalreceived through the beam selected in step 1409 among the referencesignals transmitted by the transmitting stage by changing the beam persymbol in the control slot. Next, the receiving stage completes thisprocess.

In this exemplary embodiment, the receiving stage receives the signalfrom the transmitting stage. When the receiving stage has controlinformation and data to transmit to the transmitting stage, it transmitsto the transmitting stage the control information over the control slotof the uplink frame of FIG. 5 or 6, and the data over the data slot.

As set forth above, by virtue of the frame for the communication usingbeamforming in the wireless communication system, the communication canbe fulfilled using beamforming.

In exemplary embodiments of the present invention, a frame isconstructed in a wireless communication system to distinguish a slot forat least one of a synchronization signal and common control information,a training signal slot, a control slot, and a data slot. Thus, areception performance of a mobile station can be enhanced, and areception complexity and overhead can be reduced.

The wireless communication system transmits control information bypuncturing part of the data slot. Hence, transmission efficiency of thecontrol information can be increased, thereby reducing resource waste intransmitting control information.

Since the control slot is placed in front of a subframe in the wirelesscommunication system, power consumption of a mobile station can bereduced by preventing unnecessary data reception.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A method performed by a terminal, the methodcomprising: receiving, from a base station (BS), a downlink signal usinga transmit beam of the BS, wherein the downlink signal includes asynchronization signal, a control signal fora master information block(MIB), and a reference signal; and identifying an identifier of thedownlink signal based on the reference signal, wherein the referencesignal is used to indicate the identifier of the downlink signal, andwherein the identifier of the downlink signal is associated with anorder of the downlink signal among a plurality of downlink signals in adesignated region of a frame.
 2. The method of claim 1, wherein thecontrol signal includes information on the identifier of the downlinksignal.
 3. The method of claim 1, wherein the plurality of downlinksignals are transmitted on different directions, in the designatedregion of the frame, and wherein the identifier of the downlink signalcorresponds to a beam identifier of the transmit beam of the BS.
 4. Themethod of claim 1, wherein the synchronization signal and the controlsignal are mapped on consecutive symbols, wherein the MIB includesinformation on a frame number, and wherein a number of the plurality ofdownlink signals depends on a number of slots in the designated regionof the frame.
 5. The method of claim 1, wherein symbols of the referencesignal are arranged at regular subcarrier intervals in a frequencydomain and a location of the symbols is associated with a cellidentifier, and wherein a sequence of the reference signal is associatedwith the cell identifier.
 6. A method performed by a base station (BS),the method comprising: generating a reference signal based on anidentifier of a downlink signal using a transmit beam of the BS; andtransmitting, to a terminal, the downlink signal using the transmit beamof the BS, wherein the downlink signal includes a synchronizationsignal, a control signal for a master information block (MIB), and thereference signal, wherein the reference signal is used to indicate theidentifier of the downlink signal, and wherein the identifier of thedownlink signal is associated with an order of the downlink signal amonga plurality of downlink signals in a designated region of a frame. 7.The method of claim 6, wherein the control signal includes informationon the identifier of the downlink signal.
 8. The method of claim 6,wherein the plurality of downlink signals are transmitted on differentdirections, and wherein the identifier of the downlink signalcorresponds to a beam identifier of the transmit beam of the BS.
 9. Themethod of claim 6, wherein the synchronization signal and the controlsignal are mapped on consecutive symbols, wherein the MIB includesinformation on a frame number, and wherein a number of the plurality ofdownlink signals depends on a number of slots in the designated regionof the frame.
 10. The method of claim 6, wherein symbols of thereference signal are arranged at regular subcarrier intervals in afrequency domain and a location of the symbols is associated with a cellidentifier, and wherein a sequence of the reference signal is associatedwith the cell identifier.
 11. A terminal, comprising: at least onetransceiver; and at least one processor configured to: receive, from abase station (BS) via the at least one transceiver, a downlink signalusing a transmit beam of the BS, wherein the downlink signal includes asynchronization signal, a control signal for a master information block(MIB) and a reference signal, and identify an identifier of the downlinksignal based on the reference signal, wherein the reference signal isused to indicate the identifier of the downlink signal, and wherein theidentifier of the downlink signal is associated with an order of thedownlink signal among a plurality of downlink signals in a designatedregion of a frame.
 12. The terminal of claim 11, wherein the controlsignal includes information on the identifier of the downlink signal.13. The terminal of claim 11, wherein the plurality of downlink signalsare transmitted on different directions, and wherein the identifier ofthe downlink signal corresponds to a beam identifier of the transmitbeam of the BS.
 14. The terminal of claim 11, wherein thesynchronization signal and the control signal are mapped on consecutivesymbols, wherein the MIB includes information on a frame number, andwherein a number of the plurality of downlink signals depends on anumber of slots in the designated region of the frame.
 15. The terminalof claim 11, wherein symbols of the reference signal are arranged atregular subcarrier intervals in a frequency domain and a location of thesymbols is associated with a cell identifier, and wherein a sequence ofthe reference signal is associated with the cell identifier.
 16. A basestation (BS), comprising: at least one transceiver; and at least oneprocessor configured to: generate a reference signal based on anidentifier of a downlink signal using a transmit beam of the BS; andtransmit, via the at least one transceiver to a terminal, the downlinksignal using the transmit beam of the BS, wherein the downlink signalincludes a synchronization signal, a control signal for a masterinformation block (MIB), and the reference signal, wherein the referencesignal is used to indicate the identifier of the downlink signal, andwherein the identifier of the downlink signal is associated with anorder of the downlink signal among a plurality of downlink signals in adesignated region of a frame.
 17. The base station of claim 16, whereinthe control signal includes information on the identifier of thedownlink signal.
 18. The base station of claim 16, wherein the pluralityof downlink signals are transmitted on different directions, and whereinthe identifier of the downlink signal corresponds to a beam identifierof the transmit beam of the BS.
 19. The base station of claim 16,wherein the synchronization signal and the control signal are mapped onconsecutive symbols, wherein the MIB includes information on a framenumber, and wherein a number of the plurality of downlink signalsdepends on a number of slots in the designated region of the frame. 20.The base station of claim 16, wherein symbols of the reference signalare arranged at regular subcarrier intervals in a frequency domain and alocation of the symbols is associated with a cell identifier, andwherein a sequence of the reference signal is associated with the cellidentifier.